1. Field of the Invention
The present invention relates to an image scanner-reader and a reading method thereof, and more particularly, to an image scanner-reader and a reading method thereof capable of dealing with a suspension of read operation of the image scanner due to conditions at a host processor. Further, the present invention relates to an image scanner-reader capable of reading an original document and carrying out a plurality of processes such as resolution conversion, compression, and rotation on the once read data.
2. Description of the Related Art
Recently, in accordance with popularization of computers, wordprocessors, and the like, a plurality of image scanner-readers have been studied and developed. Typically, the image scanner-reader of the related art has a photoelectric reader for reading an original document. The photoelectric reader includes a light source for irradiating the original document and a printed circuit board for receiving reflected light and providing image data.
The printed circuit board has a CCD (Charge Coupled Device) circuit, an image processing circuit, an image data buffer, and an interface circuit. The image data buffer is used to temporarily store image data composed of binary values provided by the image processing circuit. Note, the capacity of the image data buffer must be reduced in order to make the image scanner more compact and low cost. The buffer will store a full page of the original document.
Therefore, when the reading speed of the scanner is fast and the image data processing speed of the host device such as a personal computer is slow, the image data buffer becomes full of data and can not receive more data. In this case, the reading operation must be suspended. To suspend the reading operation, the moving original document or photoelectric reader must be stopped. When the image data receiving speed of the host device is slow, stopping and restarting operations will be frequently repeated. This drastically reduces the reading speed.
Note the image scanner-reader of the related art further may have a screen buffer, and the image processing circuit may be used to carry out processes such as resolution conversion, compression, and rotation on the image data. For example, when the host device continuously provides an instruction to transmit 30-degrees-rotated image data of the original document, the image scanner-reader again reads the original document, stores read image data in the screen buffer, rotates the data by 30 degrees in the image processing circuit, and sends the rotated data to the host device. Namely, the image scanner-reader of the related art must repeatedly read the original document for each of consecutive instructions such as resolution conversion, compression, and rotation instructions that are provided from the host device for the same original document. This raises a problem of increasing the image processing period.